Fixed incorrect use of executeQuery instead of executeUpdate for "DELETE" (oops)
Fixed use of c-style placeholders instead of '?' in the update next sibling
query (oops)
Removed handling a non-existent edit sheet when deleting a feed

Fixed dependencies build order in the Vienna scheme
so that 'Pods' doesn't need to be manually built by the Makefile
beforehand.
Updated the Travis CI build config to use xctool.
Still need to update the Makefile so that it uses the scheme config.

- removed instance variable for `databaseVersion`
- refactored databaseVersion to use SQLite `PRAGMA user_version` via FMDB
- split apart the monolithic `-(BOOL)initDatabase` method
- removed `prepareStringForQuery` as this is best handled by FMDB (which it does by default in `executeUpdate`)